Java程序显示Python的连续输出

Question

I would like to read the output from execute python script in time,but when I was doing this,java always waited the python until it finish(after 5 sec) all process.

I reproduced my question as following:

read.java

public static void main(String[] args) throws IOException{

    Runtime rt = Runtime.getRuntime();
    String[] commands = {"python.exe","hello.py"};  //execute the hello.py under path
    Process proc = rt.exec(commands);

    BufferedReader stdInput = new BufferedReader(new 
         InputStreamReader(proc.getInputStream()));

    BufferedReader stdError = new BufferedReader(new 
         InputStreamReader(proc.getErrorStream()));

    // read the output from the command
    System.out.println("Here is the standard output of the command:\n");
    String s = null;
    while ((s = stdInput.readLine()) != null) {
        System.out.println(s);
    }

    // read any errors from the attempted command
    System.out.println("Here is the standard error of the command (if any):\n");
    while ((s = stdError.readLine()) != null) {
        System.out.println(s);
    }

hello.py

import time

print "123\n"
time.sleep(5)  #wait 5 sec and print next line
print '456'

---update---

I rewrote my code as following,but it seemed doesn't work.

public class Hello implements Runnable {

    public void run() {
        String[] commands = { "python.exe", "hello.py" }; 
        ProcessBuilder pb = new ProcessBuilder(commands);
        pb.inheritIO();
        try {
            Process p = pb.start();
            int result = p.waitFor();
        } catch (IOException | InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String args[]) {
        (new Thread(new Hello())).start();
    }

}

Answer 1

I would prefer ProcessBuilder and inheritIO , something like

String[] commands = { "python.exe", "hello.py" }; 
ProcessBuilder pb = new ProcessBuilder(commands);
pb.inheritIO();
try {
    Process p = pb.start();
    int result = p.waitFor();
} catch (IOException | InterruptedException e) {
    e.printStackTrace();
}

For your current solution to work, you would need to handle the IO in non-blocking threads.